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JAMB Mathematics 1997 Question 23

Question 23

Matrices and Determinants

Determine x + y if (2 −3 / −1 4)(x / y) = (−1 / 8)
(The 2 × 2 matrix has rows 2, −3 and −1, 4; the column vectors are (x, y) and (−1, 8).)

  1. A.3
  2. B.4
  3. C.7
  4. D.12
Show the answer and explanation

Answer: C (7)

Explanation

The equations are 2x − 3y = −1 and −x + 4y = 8. Solving gives y = 3 and x = 4, so x + y = 7.